The present invention relates to a diaphragm assembly for a diaphragm pump of an inhaling apparatus compressor with the features of the main claim of patent claim 1.
Such a diaphragm assembly is known from the German Patent DE 86 26 979.9. As shown in FIG. 7, a flat diaphragm 100 is clamped between an upper diaphragm disc 101 and a lower diaphragm disc 102. This takes place with the aid of a countersunk screw 103 which is guided through openings in the center of the upper diaphragm disc, the diaphragm and the lower diaphragm disc so that they can be screwed with a connecting rod for actuation of the diaphragm. An intermediate ring 104 is generally inserted between the lower diaphragm disc and the connecting rod.
As shown in FIG. 8, such a diaphragm assembly is used in a diaphragm compressor which is formed from a compressor housing with a housing lower member 105 and a housing upper member 106. A circulating groove is provided in the housing upper member 106 which receives the outer rim of the flexible diaphragm. The diaphragm is held in its position inside the groove by pressing between the housing lower member and the housing upper member. The two diaphragm discs which abut against the upper and lower side of the diaphragm are rigid against distortion so that the diaphragm therebetween can merely be elastically deformed in its free rim region.
Such diaphragm assemblies are used for conveying and compressing fluid and gaseous media, for example in inhaling apparatuses. It is generally endeavoured to achieve a construction for the largest possible range of use so that with a rigidly predetermined drive performance a highest possible pressure and weight rate of flow must be achieved. This is generally achieved by adaptation of the clearance volume directly over the clamped rim of the diaphragm and by an enlargement of the unstiffened rim region of the flexible diaphragm.
However, on account of the enlarged rim region of the flexible diaphragm, the noise development also increases, which is especially critical in the case of use in inhaling apparatuses. Care must be taken here that the therapeutical effect for the patient to be treated is not impaired by an excessively high noise development.
Furthermore, as shown in FIG. 7, the diaphragm assembly according to the prior art involves not inconsiderable problems with respect to production, which remain unsolved until now. If, as explained above, the diaphragm is clamped between the upper diaphragm disc and the lower diaphragm disc with the aid of a countersunk screw,dependent on the force with which the countersunk screw is tightened different radii of the diaphragm occur after clamping, and thus different pretensions in the diaphragm material.
It is moreover difficult to achieve a uniform clamping of the flexible diaphragm in different diaphragm assemblies, and high tolerances occur in the production of the diaphragm assemblies. In particular in the cases in which the diaphragm is clamped especially rigidly the screw must be tightened with a high force, which is especially strenous and fatiguing for the personnel. This mode of procedure is as a whole intricate and time-consuming, so that on account of the increasing quantities in which such diaphragm assemblies are manufactured there is an acute necessity for action.
The object on which the present invention is based consists in providing a diaphragm assembly which can be simply produced with improved production tolerances and which simultaneously reveals favorable operating properties and has a long life.
According to the invention, this object is solved in a diaphragm assembly for a diaphragm pump of the initially described type in that on the outer periphery of the flexible diaphragm a ring-shaped portion is bent towards the axis of the securement member, and along the upper rim of the second opening a stop member is formed against which the inside rim of the first opening of the flexible diaphragm abuts.
An important advantage of the invention lies in the fact that on account of the bending of the rim portion of the flexible diaphragm, a shaping of the flexible diaphragm is achieved from the very beginning which is necessary for a regular operation of the diaphragm assembly, so that when clamping the flexible diaphragm between the upper and lower diaphragm discs, considerably less force needs to be applied, with the result that the personnel is relieved and the production process accelerated.
A further important advantage of the invention is that the flexible diaphragm abuts against a stop member on the inner side of its opening. This leads to the fact that upon alignment of the upper and lower diaphragm discs and the flexible diaphragm practically no more deviations can occur and the production tolerances can be considerably improved.
When, as described above, the outer rim of the flexible diaphragm is pressed into a groove of the housing upper member between the housing upper member and housing lower member, the unstiffened rim region of the flexible diaphragm projects toroidally into the clearance volume so that this is reduced. Accordingly, the diaphragm assembly according to the invention permits an improved noise behaviour since due to the reduced clearance volume less noise disturbances occur as a whole.
The unstiffened rim region of the flexible diaphragm projecting toroidally into the clearance volume of the diaphragm compressor can also roll off directly upon an up and down movement of the flexible diaphragm. On account of this rolling off procedure, the deformation in the flexible diaphragm occurring during the up and down movement can be reduced, so that the life of the flexible diaphragm is considerably lengthened. Furthermore, the toroidal course of the unstiffened rim region of the flexible diaphragm effects a continuous change of the clearance volume which leads to the fact that the operating pressure during compression of fluid or gaseous media is increased and the maximum pressure during operation reduced. This also results in a flat characteristic curve.
In a further especially preferred embodiment of the diaphragm assembly according to the invention, at least one centralizing groove for the flexible diaphragm is provided in the lower diaphragm disc between the outer periphery and the stop member, the flexible diaphragm comprising at least one holding ring in a corresponding manner. In this embodiment, the alignment of the individual components of the diaphragm assembly to one another is further improved, since independent of the force with which the flexible diaphragm is clamped between the upper and the lower diaphragm disc, a deformation of the flexible diaphragm in the area of the clamping position is excluded.
In an especially advantageous development of the diaphragm assembly according to the invention, it is provided that the lower diaphragm disc has a torus on its outer periphery. This advantageously favors the above-described rolling off procedure during the up and down movement of the flexible diaphragm.